The broad spectrum antimicrobial agent, 5-chloro-2-(2,4-dichlorophenoxy)phenol (also referred to as “triclosan” or “Irgasan®”, which is Ciba Specialty Chemical's brand name for triclosan), has been commonly used since the early 1970's for personal hygiene products, including soap, toothpaste, deodorant, and for household and industrial cleaning products. Although at high concentrations triclosan is a biocide, at lower levels it functions as a bacteriostatic agent.
Despite the long history of antimicrobial use, triclosan alone has not been routinely used as a selective agent in differentiation media for preferential growth of particular bacterial species. U.S. Pat. No. 5,447,849 to Toora teaches the use of a combination of cefsulodin and triclosan for selective growth of Yersinia enterocolitica. U.S. Pat. No. 5,741,663 to Russell teaches the use of triclosan in combination with carbenicillin and nitrofurantoin for selective growth of Pseudomonas fluorescens. US Patent Application Publication 2010/0278847 to Good et al. teaches the addition of triclosan in the range of 100 nM to 10 μM to culture medium (which was also supplemented with ampicillin) for distinguishing genetically modified (transformed) E. coli showing vector-mediated expression of the gene for enoyl-ACP reductase (fab1). There is no disclosure in Good et al. relating to culture of naturally-occurring bacteria and/or fungi of the type typically found in environmental, industrial or medical samples.